1. Field of the Invention
The invention relates in general to an active/self-sensing compensating hydrostatic bearing and a hydrostatic bearing module using the same, and more particularly to a hydrostatic bearing using a compensator for performing an active compensation and a hydrostatic bearing module using the same.
2. Related Art
Bearings are indispensable key components in precise mechanical machine tools. A non-contact-type hydrostatic bearing can provide the high rigidity and high precision properties for the submicron machining technology, and is thus frequently used in a large-scale machine tool. The hydrostatic bearing always works under the liquid lubrication from the start to the stop. That is, the normal oil film fluid may also be established in the zero-speed state, and the bearing does not directly contact the spindle, so that the bearing has the long lifetime and requires the low starting power. In addition, the hydrostatic bearing also has the advantages of the high rotation precision and the high stiffness of the oil film, and is thus widely applied to the heavy, precise and high-efficiency machine and apparatus.
The hydrostatic bearing keeps the stable oil film pressure using an external oil supply system to provide a pressurized fluid and using the multi-pocket structure design in the bearing. The pressure difference between the pockets is the source for the bearing to provide the load-carrying capacity. For the constant-pressure oil supply system with the single pressure supply, the bearing must have a pressure compensator for compensating the pressure in the pocket, and this compensator is referred to as a restrictor. Different types of restrictors provide different bearing performances. More particularly, the rigidity of the bearing is mainly based on the restrictor, so the restrictor is the main component in the hydrostatic bearing. The restrictors used in the industry can be classified into a fixed restrictor and an active restrictor. The fixed restrictor may be a capillary-type restrictor, a slit restrictor, an orifice restrictor or the like. The geometric shape of the fixed restrictor cannot change according to the change of the operation condition. The internal geometric structure of the active restrictor, such as a slide valve restrictor or a film feedback restrictor, is automatically adjusted due to the change of the external load or the pocket pressure. If the design and adjustment are made properly, the active restrictor can have the load-carrying capacity and the rigidity higher than those of the fixed restrictor. However, since the conventional hydrostatic bearing system always has the externally connected restrictor, which is connected to the pocket through an oil conduit, the delay is caused in the compensation response due to the oil conduit between the restrictor and the pocket. Therefore, the conventional hydrostatic bearing system has the problem of operation delay. In addition, the conventional capillary-type restrictor or aperture restrictor, for example, has the poor static rigidity because the restrictor flow resistance caused by the capillary-type restrictor is a constant and cannot be adjusted to perform the compensation according to the variation of the pocket pressure.
Thus, an active compensation restrictor bearing is provided to achieve the high static and dynamic rigidity and the stable behavior, so that the new possibility can be provided to the actual technical application.